The present invention relates to imaging output devices, and more particularly to an apparatus (and method) for outputting halftone-dot images automatically from rasterized digital image data, by an image transfer process between a donor material and a receiver material, in an internal drum imaging device. The invention has applications in both imagesetting and direct digital color proofing, hereinafter DDCP, and platemaking.
In image transfer processes such as thermal melt transfer, dye sublimation-type thermal transfer, dye fusion-type thermal transfer, and ablation transfer, a donor material is superimposed onto a receiver material so that imagewise exposure of the donor material by a radiant energy or heat, such as a laser beam, causes transfer of the donor material onto the receiver material upon receipt of a sufficient amount of energy. An example of such transfer materials and applications for preparing and using them are disclosed in U.S. Pat. Nos. 5,232,817 and 5,238,778. For DDCP applications the imagewise exposure usually occurs in a series of color separations such colors as cyan, yellow, magenta, and black (CYMK). For each color separation, a correspondingly colored donor sheet is superimposed onto the receiver, exposed to transfer the respective color separation of the image onto the receiver material, and then removed. The image is thereby transferred onto the receiver material and a color proof is obtained.
Heretofore, DDCP devices have been flatbed and external drum type proofing devices, in which the receiver and donor materials are superimposed on a flat bed or a rotary drum support. Prior external drum devices are disclosed in U.S. Pat. Nos. 5,164,742 and 5,341,159. The methods and mechanisms for handling the receiver and donor materials differ for each type of support to fulfill such requirements as applying the materials onto the support, ensuring full, intimate contact between the receiver and donor sheet, peeling the donor from the receiver, and transporting the completed proof without damaging the image. A common factor among DDCP devices is that the color donor sheets must be sequentially superimposed onto a single receiver sheet and then removed without disturbing the receiver sheet on the support to ensure registration of the transferred partial images that create the final proof. While the prior art devices have capably serviced the graphic arts and printing industries, inherent advantages are realized in a thermal imaging device which relies on an internal drum type material support, as will become apparent in the following description of the invention, for applications in proofing, imagesetting and platemaking.
It is therefore a general object of the invention to perform image transfer processes such as dye sublimation-type thermal transfer, dye fusion-type thermal transfer, and ablation transfer, as well as conventional imagesetting and dry processes, using the respective required materials, to output films, color proofs, and/or printing plates in a single imaging device.
It is a general object of the present invention to generate high quality digital proofs in an automated internal drum proofing device.
It is a general object of the invention to provide an internal drum support surface for adhering a receiver sheet upon and sequentially superimposing a series of color donor material for transfer of respective color separations of an image to create a color proof on the receiver material while registered to the drum surface.
It is an object of the invention to achieve intimate contact between a donor material and a receiver material used in a thermal imaging process, particularly on an internal drum material support.
It is further an object of the invention to provide an apparatus specifically for transporting the donor and receiver materials without damaging the sensitive sides thereof.